Federal Reserve Bank of Boston President Eric Rosengren said the central bank’s third round of quantitative easing will bolster the housing market and economy while helping to prevent lasting damage to the labor market.

“It is important to generate faster growth to avoid what some call labor market ‘scarring’ — where long-duration unemployment becomes ingrained into our labor market,” Rosengren said Wednesday, according to the text of a speech to be delivered in Quincy, Mass.

Rosengren endorsed the Fed’s strategy announced last week of buying $40 billion a month of mortgage-backed securities and echoed arguments from Chairman Ben S. Bernanke about the urgency of addressing the nation’s jobs shortfall, which has left unemployment stuck above 8 percent since February 2009.

“Long periods of unemployment frequently deplete the savings of the unemployed, make re-employment harder” and “may lead to skills becoming less than current,” Rosengren said.

The Federal Open Market Committee said in its September 13 statement that economic conditions would likely warrant holding the Fed’s target interest rates near zero through at least mid-2015 and that monetary stimulus will remain appropriate for a “considerable time” after growth strengthens.

Rosengren said that a “very challenging economic climate confronts us all” and that monetary policy is not “a panacea.” He added that appropriate fiscal policies in the U.S. and a pickup in global growth could “both provide significant positive effects, and shorten the time needed for unconventional monetary-policy actions like those we have announced.”

The decision to purchase mortgage bonds will place downward pressure on mortgage rates and will thus help improve home sales and prices, Rosengren said.

The housing market has already been improving, a trend confirmed by reports Tuesday showing that sales of previously owned homes and work on single-family projects climbed in August to the highest levels in two years.

Purchases of existing houses increased 7.8 percent to a 4.82 million annual rate in August, the most since May 2010, figures from the National Association of Realtors showed yesterday in Washington. Commerce Department data showed builders began work on the most one-family homes since April 2010.

Confidence among home builders climbed to the highest level in more than six years, according to a Sept. 18 report of the National Association of Home Builders/Wells Fargo builder sentiment index.

Rosengren joined Chicago Fed President Charles Evans and the New York Fed’s William C. Dudley in defending the third round of quantitative easing. Evans said in a speech in Ann Arbor, Mich., on Sept. 18 that the Fed’s actions will help strengthen a pace of growth that has been “disappointing” and help counteract “greater downside risks posed by the slowdown in global economic growth, the economic turmoil in Europe and the fast-approaching U.S. fiscal cliff.” If Congress doesn’t act, more than $600 billion in automatic tax increases and spending cuts will take effect starting in January.

Dudley said Sept. 18 that without further action from the Fed, growth would remain “unacceptably slow.” Dudley also said monetary policy isn’t a “panacea” although a “nudge in the right direction will move us closer to a self-reinforcing cycle of more hiring, more spending, more growth, and more investment.”

Fed Presidents rotate voting on monetary policy, with Rosengren, 55, voting next year. He has led the Boston Fed since 2007. Rosengren’s remarks were titled “Acting to Avoid a ‘Great Stagnation.’”

“I am very pleased that monetary-policy makers in the U.S. are proving willing to take difficult actions like these rather than accept the possibility of a long, slow recovery turning into a stagnation that someday earns the dubious title of ‘Great,’” he said.